Audio encoder device and an audio decoder device having efficient gain coding in dynamic range control

ABSTRACT

An audio encoder device includes an audio encoder configured for producing an encoded audio bitstream from an audio signal having consecutive audio frames; a dynamic range control encoder configured for producing an encoded dynamic range control bitstream from an dynamic range control sequence corresponding to the audio signal and having consecutive dynamic range control frames, wherein each dynamic range control frame of the dynamic range control frames has one or more nodes, wherein each node of the one or more nodes has gain information for the audio signal and time information indicating to which point in time the gain information corresponds.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending U.S. patent applicationSer. No. 16/404,503, filed May 6, 2019, which in turn is a continuationof copending International Application No. PCT/EP2015/055945, filed Mar.20, 2015, which is incorporated herein by reference in its entirety, andadditionally claims priority from European Application No. EP14161605.2, filed Mar. 25, 2014, which is also incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

Dynamic range control (DRC) in the context of this document refers to adigital signal processing technique to reduce the dynamic range of audiosignals in a controlled way [1]. The desired reduction of the dynamicrange is achieved by reducing the level of loud sound components and/oramplifying soft parts of the audio signals.

A typical application for DRC is to adapt the dynamic properties of anaudio signal to a listening environment. For example, when listening tomusic in noisy environment, the dynamic range should be reduced in orderto allow for an overall signal amplification without driving theresulting amplified signal into clipping. In this case, high signalpeaks should be attenuated, e.g. by means of a limiter. Additionally,soft signal components should be amplified relative to the loud parts inorder to improve their intelligibility in a noisy listening environment.

SUMMARY

According to an embodiment, an audio encoder device may have: an audioencoder configured for producing an encoded audio bitstream from anaudio signal including consecutive audio frames; a dynamic range controlencoder configured for producing an encoded dynamic range controlbitstream from an dynamic range control sequence corresponding to theaudio signal and including consecutive dynamic range control frames,wherein each dynamic range control frame of the dynamic range controlframes includes one or more nodes, wherein each node of the one or morenodes includes gain information for the audio signal and timeinformation indicating to which point in time the gain informationcorresponds; wherein the dynamic range control encoder is configured insuch way that the encoded dynamic range control bitstream includes foreach dynamic range control frame of the dynamic range control frames acorresponding bitstream portion; wherein the dynamic range controlencoder is configured for executing a shift procedure, wherein one ormore nodes of the nodes of one reference dynamic range control frame ofthe dynamic range control frames are selected as shifted nodes, whereina bit representation of each of the one or more shifted nodes of the onereference dynamic range control frame is embedded in the bitstreamportion corresponding to the dynamic range control frame subsequent tothe one reference dynamic range control frame.

According to another embodiment, an audio decoder device may have: anaudio decoder configured for decoding an encoded audio bitstream inorder to reproduce an audio signal including consecutive audio frames; adynamic range control decoder configured for decoding an encoded dynamicrange control bitstream in order to reproduce an dynamic range controlsequence corresponding to the audio signal and including consecutivedynamic range control frames; wherein the encoded dynamic range controlbitstream includes for each dynamic range control frame of the dynamicrange control frames a corresponding bitstream portion; wherein theencoded dynamic range control bitstream includes bit representations ofnodes, wherein each bit representation of one node of the nodes includesgain information for the audio signal and time information indicating towhich point in time the gain information corresponds; wherein theencoded dynamic range control bit stream includes bit representations ofshifted nodes selected from the nodes of one reference dynamic rangecontrol frame of the dynamic range control frames, which are embedded ina bitstream portion corresponding to the dynamic range control framesubsequent to the one reference dynamic range control frame; and whereinthe dynamic range control decoder is configured for decoding the bitrepresentation of each shifted node of the shifted nodes selected fromthe nodes of the one reference dynamic range control frame of thedynamic range control frames in order to reproduce each shifted node ofthe shifted nodes selected from the nodes of the one reference dynamicrange control frame of the dynamic range control frames.

According to another embodiment, a system including an audio encoderdevice may have: an audio encoder configured for producing an encodedaudio bitstream from an audio signal including consecutive audio frames;a dynamic range control encoder configured for producing an encodeddynamic range control bitstream from an dynamic range control sequencecorresponding to the audio signal and including consecutive dynamicrange control frames, wherein each dynamic range control frame of thedynamic range control frames includes one or more nodes, wherein eachnode of the one or more nodes includes gain information for the audiosignal and time information indicating to which point in time the gaininformation corresponds; wherein the dynamic range control encoder isconfigured in such way that the encoded dynamic range control bitstreamincludes for each dynamic range control frame of the dynamic rangecontrol frames a corresponding bitstream portion; wherein the dynamicrange control encoder is configured for executing a shift procedure,wherein one or more nodes of the nodes of one reference dynamic rangecontrol frame of the dynamic range control frames are selected asshifted nodes, wherein a bit representation of each of the one or moreshifted nodes of the one reference dynamic range control frame isembedded in the bitstream portion corresponding to the dynamic rangecontrol frame subsequent to the one reference dynamic range controlframe, and an inventive audio decoder device.

According to another embodiment, a method for operating an audio encodermay have the steps of: producing an encoded audio bitstream from anaudio signal including consecutive audio frames; producing an encodeddynamic range control bitstream from an dynamic range control sequencecorresponding to the audio signal and including consecutive dynamicrange control frames, wherein each dynamic range control frame of thedynamic range control frames includes one or more nodes, wherein eachnode of the one or more nodes includes gain information for the audiosignal and time information indicating to which point in time the gaininformation corresponds, wherein the encoded dynamic range controlbitstream includes for each dynamic range control frame of the dynamicrange control frames a corresponding bitstream portion; executing ashift procedure, wherein one or more nodes of the nodes of one referencedynamic range control frame of the dynamic range control frames areselected as shifted nodes, wherein a bit representation of each of theone or more shifted nodes of the one reference dynamic range controlframe is embedded in the bitstream portion corresponding to the dynamicrange control frame subsequent to the one reference dynamic rangecontrol frame.

According to another embodiment, a method for operating an audio decodermay have the steps of: decoding an encoded audio bitstream in order toreproduce an audio signal including consecutive audio frames; decodingan encoded dynamic range control bitstream in order to reproduce andynamic range control sequence corresponding to the audio signal andincluding consecutive dynamic range control frames; wherein the encodeddynamic range control bitstream includes for each dynamic range controlframe of the dynamic range control frames a corresponding bitstreamportion; wherein the encoded dynamic range control bitstream includesbit representations of nodes, wherein each bit representation of onenode of the nodes includes gain information for the audio signal andtime information indicating to which point in time the gain informationcorresponds; wherein the encoded dynamic range control bit streamincludes bit representations of shifted nodes selected from the nodes ofone reference dynamic range control frame of the dynamic range controlframes, which are embedded in a bitstream portion corresponding to thedynamic range control frame subsequent to the one reference dynamicrange control frame; and wherein the bit representation of each shiftednode of the shifted nodes selected from the nodes of the one referencedynamic range control frame of the dynamic range control frames isdecoded in order to reproduce each shifted node of the shifted nodesselected from the nodes of the one reference dynamic range control frameof the dynamic range control frames.

Another embodiment may have a non-transitory digital storage mediumhaving a computer program stored thereon to perform any of the inventivemethods.

The invention addresses the situation of audio transmission using codingof the audio signal, wherein the gain information is not directlyapplied to the audio signal, but also encoded and transmitted togetherwith the encoded audio signal. At the decoder, both, the audio signaland the gain information, may be decoded and the gain information may beapplied to the corresponding audio signal. As explained more detailedbelow, the invention achieves an efficient coding of the gaininformation. More precisely, it avoids bitrate peaks in the encodeddynamic range control bitstream.

The process of applying dynamic range control to an audio signal can beexpressed by a simple multiplication of the audio signal x(k) by atime-variant gain value g(k):

y(k)=g(k)×(k)  (1)

where k denotes a sample time index. The value of the gain g(k) may becomputed, e.g. based on a short-term estimate of the root-mean square ofthe audio signal x(k). More details about strategies to determinesuitable gains values are discussed in [1]. In the following we refer tothe time-variant gains g(k) as a gain sequence.

In the following, the coding of dynamic range control gain sequences isexplained. First, the dynamic range control gain sequence is dividedinto so-called dynamic range control frames of gain samples, containinga fixed number of gain samples. Usually, a temporal frame size for thedynamic range control frames is chosen to be equal to the temporal sizeof an audio frame of the corresponding audio encoder. Within eachdynamic range control frame, so-called nodes are selected,advantageously on a uniform time grid.

The spacing of this grid defines the highest available time resolution,i.e., the minimum distance in samples between two nodes equals tosamples having the highest available time resolution. Each node isrepresented by the sample position within the dynamic range controlframe, the gain information, which may be expressed as a gain value, forthat position and optionally information about the slope of the gainvalues at the node positions. For the following discussion it will beuseful to define the maximum number of nodes that can be selected withinone frame.

The dynamic range control encoder encodes the gain information from thenodes, e.g., by using quantized differential values of pairs ofconsecutive gain nodes. At the decoder, the original gain sequence isreconstructed as good as possible by using spline interpolation orlinear interpolation based on the transmitted information of the nodes(gain value, sample position within the dynamic range control frame, andslope information if applicable).

An efficient approach for encoding the dynamic range control gainsequence is to use a quantized value of the gain difference (typicallyin dB) of pairs of consecutive nodes, as well as the time difference ofthe sample positions of these nodes within the considered dynamic rangecontrol frame. The slope information is usually not represented as adifference between two nodes. Since there is no preceding node for thefirst node within a frame, its gain value is not encoded in adifferential way, but the values are encoded explicitly. The timedifference of the first node is usually determined as the offset to thebeginning of the dynamic range control frame.

The encoder may then assign a fixed code word e.g. of a pre-definedHuffman table (code book) to each of the gain and time differences ofpairs of nodes.

At the dynamic range control decoder, the dynamic range controlbitstream is decoded and the relevant information (gain value, sampleposition within the dynamic range control frame, and slope informationif applicable) at the positions of the transmitted nodes isreconstructed. The gain values for the remaining gain samples within aframe are obtained by interpolation between pairs of transmitted anddecoded nodes. The interpolation can be based on splines if the slopeinformation of the gain nodes has been transmitted or, alternatively,using linear interpolation if only the gain differences between pairs ofnodes are available and the slope information is discarded.

In principle, dynamic range control encoder/decoder chains can beoperated in two modes. The so-called full-frame mode refers to the casewhere after decoding of a received dynamic range control bitstream,corresponding to a reference dynamic range control frame, the gains ateach sample position of the reference dynamic range control frame can beimmediately determined after interpolation based on the decoded nodes.This implies that a node has to be transmitted at each frame border,i.e., at the sample position corresponding to the last sample of thereference dynamic range control frame. If the dynamic range controlframe length is N this means the last transmitted node has to be locatedat the sample position N within the reference dynamic range controlframe.

The invention avoids this disadvantage as it is based on the secondmode, which is referred to as “delay mode”. In this case, there is noneed for transmitting a node for the last sample position within thereference dynamic range control frame. Therefore, the dynamic rangecontrol decoder has to wait for decoding the dynamic range control framesubsequent to the reference dynamic range control frame in order toperform the interpolation that may be used of all gain values followingthe last node within reference dynamic range control frame. This isbecause the information of the first node of the subsequent dynamicrange control frame has to be known to perform the interpolation betweenthe last node of the reference dynamic range control frame and the firstnode of the subsequent dynamic range control frame in order to determinethe gain value in between via interpolation.

In practice the delay caused by using the delay mode for coding of thedynamic range control information is not an issue. This is because audiocodecs that commonly accompany the dynamic range control coding schemealso introduce an inherent delay of one audio frame when subsequentlyapplying the encoding and decoding steps. Important examples of suchaudio codecs are the ISO/IEC 13818-7, Advanced Audio Coding (MPEG-2AAC), ISO/IEC 14496-3, subpart 4 (MPEG-4 AAC), or ISO/IEC 23003-3, part3, Unified Speech and Audio Coding (USAC). Such audio coding schemes usethe reference audio frame and the audio frame subsequent to thereference audio frame in order to compute (using an overlap-addstructure) the correct audio samples corresponding to the referencedynamic range control audio frame.

It is important to note that the number of nodes that may be used forsufficiently approximating the original dynamic range control gainsequence significantly varies from dynamic range control frame todynamic range control frame. That results from the fact that more nodesmay be used for representing highly time-variant gains compared to thecase where only slowly changing gain values have to be encoded. Thisobservation implies that the bitrate that may be used to transmit gainsequences can vary significantly from frame to frame. Some frames mayinvolve a large number of nodes being encoded, resulting in high bitratepeaks. This is not desirable, especially, when the audio signal and thedynamic range control gain sequence are transmitted in a joint bitstreamhaving the encoded dynamic range control bitstream and the encoded audiobitstream, which should have almost constant bitrate. Then, a peak inthe dynamic range control related bitrate reduces the available bitratefor the audio encoder, which often result in a degradation of the audioquality after decoding. However, with the current state-of-the-artmethods for the coding of dynamic range control gain sequences, areduction of the dynamic range control related bitrate in a certainframe is only achieved by reducing the number of nodes that are selectedto represent the gain sequence within that frame. This again may lead tolarge errors between the original gain sequence and the one that isreconstructed after the dynamic range control decoding process. Theinvention overcomes these disadvantages by reducing the peak bitrates ofencoded dynamic range control bitstream without increasing the errorbetween the original and the reconstructed dynamic range controlsequence.

In this section, the coding of dynamic range control gain sequencesaccording to the invention is presented. The invention allowscontrolling the peak bitrate that may be used for a reference dynamicrange control frame without changing the resulting bitstream sequencecompared to the case where the proposed method is not used. The proposedapproach exploits the inherent delay of one frame introduced bystate-of-the-art audio coders to reduce peaks of number of nodes withinone frame by distributing the transmission of some of the nodes to thenext subsequent dynamic range control frame. The details of the proposedmethod are presented in the following.

As explained above, when combined with an audio coding scheme thatintroduces a frame delay relative to the dynamic range control gains,the decoded dynamic range control gains are delayed by one frame beforebeing applied to the audio signal. This means that the nodes of thereference dynamic range control frame are applied to the valid audiodecoder output at dynamic range control frame subsequent to thereference dynamic range control frame. This implies that in the defaultdelay mode it is sufficient to transmit the nodes of the referencedynamic range control frame together with the nodes of the dynamic rangecontrol frame subsequent to the reference dynamic range control frameand apply the corresponding dynamic range control gains without a delaydirectly to the corresponding audio output signal at the decoder.

This fact is exploited in the invention in order to reduce the maximumnumber of nodes transmitted within one dynamic range control frame.According to the invention some of the nodes of the reference dynamicrange control frame are shifted to the subsequent dynamic range controlframe, which may be done before encoding. As it will be discussed in thefollowing, the shifted nodes may be “preceding” the first node in thesubsequent dynamic range control frame only for the encoding of the gaindifferences and the slope information. For the coding of the timedifference information, a different method may be applied.

According to an advantageous embodiment of the invention the shiftprocedure is initiated in case that a number of the nodes of thereference dynamic range control frame is greater than a predefinedthreshold value.

According to an advantageous embodiment of the invention the shiftprocedure is initiated in case that a sum of a number of the nodes ofthe reference dynamic range control frame and a number of shifted nodesfrom the dynamic range control frame preceding the reference dynamicrange control frame to be embedded in the bitstream portioncorresponding to the reference dynamic range control frame is greaterthan a predefined threshold value.

According to an advantageous embodiment of the invention the shiftprocedure is initiated in case that a sum of a number of the nodes ofthe reference dynamic range control frame and a number of shifted nodesfrom the dynamic range control frame preceding the reference dynamicrange control frame to be embedded in the bitstream portioncorresponding to the reference dynamic range control frame is greaterthan a number of the nodes of the dynamic range control frame subsequentto the reference dynamic range control frame.

Independent from the conditions defined under which the shift procedureis initiated, the first node of the reference dynamic range controlframe should not be shifted to the subsequent dynamic range controlframe as its value is needed for interpolation of the gain controlvalues at the beginning of the reference dynamic range control frame.Furthermore, a node should be shifted only one time in order to avoid adelay when decoding the bitstream.

According to an advantageous embodiment of the invention the timeinformation of the one or more nodes is represented in such way that theone or more shifted nodes may be identified by using the timeinformation.

According to an advantageous embodiment of the invention the timeinformation of the one or more shifted nodes is represented by a sum ofa time difference from a beginning of the dynamic range control frame towhich the respective node belongs to the temporal position of therespective node within the dynamic range control frame to which therespective node belongs and an offset value being greater than or equalto a temporal size of the dynamic range control frame subsequent to therespective dynamic range control frame.

According to an advantageous embodiment of the invention the gaininformation of the bit representation of the shifted node, which is at afirst position of the bitstream portion corresponding to the dynamicrange control frame subsequent to the reference dynamic range controlframe, is represented by an absolute gain value and wherein the gaininformation of each bit representation of the shifted nodes at aposition after the bit representation of the node, which is at the firstposition of the bitstream portion corresponding to the dynamic rangecontrol frame subsequent to the reference dynamic range control frame,is represented by a relative gain value which is equal to a differenceof a gain value of the bit representation of the respective shifted nodeand the gain value of the bit representation of the node, which precedesthe bit representation of the respective node.

According to an advantageous embodiment of the invention, in case thatthe bit representations of one or more shifted nodes of the referencedynamic range control frame is embedded in the bitstream portioncorresponding to the dynamic range control frame subsequent to thereference dynamic range control frame, the gain information of the bitrepresentation of the node of the subsequent dynamic range control frameat a first position of the bitstream portion corresponding to thedynamic range control frame subsequent to the reference dynamic rangecontrol frame after the one or more positions of the bit representationsof the one or more shifted nodes is represented by a relative gain valuewhich is equal to a difference of a gain value of the bit representationof the respective node and a gain value of the bit representation of theshifted node, which precedes the bit representation of the respectivenode.

According to an advantageous embodiment of the invention a temporal sizeof the audio frames is equal to a temporal size of the dynamic rangecontrol frames.

According to an advantageous embodiment of the invention the one or morenodes of one of the dynamic range control frame are selected from auniform time grid.

According to an advantageous embodiment of the invention each node ofthe one or more nodes comprises slope information.

According to an advantageous embodiment of the invention the dynamicrange control encoder is configured for encoding the nodes using anentropy encoding technique, such as Huffman coding or arithmetic coding.

The encoder may assign a fixed code word e.g. of a pre-defined Huffmantable (code book) to each of the gain and time differences of pairs ofnodes. Examples of suitable Huffman tables for encoding the timedifferences of pairs of consecutive nodes are given in Table 1 and Table2, respectively.

TABLE 1 Example of a Huffman table for the coding of time differences ofDRC gain nodes. Time difference Time difference tDrcDelta Codeword size[bits] binary encoding in multiples of deltaTmin 1 0x000 nNodesMax 30x004 1 5 0x014+(a−2) a=[2..5] 6 0x030+(a−6) a=[6..13] 12 0xE00+(a−14)a=[ 14..2*nNodesMax−1 ]

TABLE 2 Example of a Huffman table for the coding of time differences ofDRC gain nodes, where Z = cell(log2(2*nNodesMax)) Time difference inmultiples of del- Encoding Size taTmin Range 00 2 bits tDrcDelta = 1 1{01, μ} {2 bits, 2 tDrcDelta = μ + 2 2...5 bits} {10, μ} {2 bits, 3tDrcDelta = μ + 6 6...13 bits} {11, μ} {2 bits, Z tDrcDelta = μ + 1414...2*nNodesMax bits}

In a further aspect of the invention the objective is achieved by anaudio decoder device comprising:

an audio decoder configured for decoding an encoded audio bitstream inorder to reproduce an audio signal comprising consecutive audio frames;

a dynamic range control decoder configured for decoding an encodeddynamic range control bitstream in order to reproduce an dynamic rangecontrol sequence corresponding to the audio signal and comprisingconsecutive dynamic range control frames;

wherein the encoded dynamic range control bitstream comprises for eachdynamic range control frame of the dynamic range control frames acorresponding bitstream portion;

wherein the encoded dynamic range control bitstream comprises bitrepresentations of nodes, wherein each bit representation of one node ofthe nodes comprises gain information for the audio signal AS and timeinformation indicating to which point in time the gain informationcorresponds;

wherein the encoded dynamic range control bit stream comprises bitrepresentations of shifted nodes selected from the nodes of onereference dynamic range control frame of the dynamic range controlframes, which are embedded in a bitstream portion corresponding to thedynamic range control frame subsequent to the one reference dynamicrange control frame, wherein the bit representation of each remainingnode of the nodes of the one reference dynamic range control frame ofthe dynamic range control frames is embedded into the bitstream portioncorresponding to the one reference dynamic range control frame; and

wherein the dynamic range control decoder is configured for decoding thebit representation of each remaining node of the remaining nodes of theone reference dynamic range control frame of the dynamic range controlframes in order to reproduce each remaining node of the one referencedynamic range control frame of the dynamic range control frames, fordecoding the bit representation of each shifted node of the shiftednodes selected from the nodes of the one reference dynamic range controlframe of the dynamic range control frames in order to reproduce eachshifted node of the shifted nodes selected from the nodes of the onereference dynamic range control frame of the dynamic range controlframes and for combining the reproduced remaining nodes and thereproduced shifted nodes in order to reconstruct the reference dynamicrange control frame.

The dynamic range control decoder receives the dynamic range controlbitstream. The dynamic range control bitstream, which corresponds to thenode information (sample position, gain value, and slope information ifapplicable), may be decoded in the following way:

A value for the time difference between two nodes (e.g. as an integermultiple of the minimum distance between two nodes) is determined fromthe received code word based e.g. on the rules shown in a Huffman codebook. The corresponding sample position of the currently decoded node isobtained by adding the time difference value to the sample positionvalue computed for the previous node.

After decoding the nodes of the reference dynamic range control framethe nodes of the subsequent dynamic range control frame are decoded.

If the determined sample position within the subsequent dynamic rangecontrol frame corresponds to a value that is larger than the length of asubsequent dynamic range control frame, the dynamic range controldecoder knows that the current temporal node information refers to anode originally located in the reference dynamic range control frame.

To obtain the correct sample position within the reference dynamic rangecontrol frame, an offset is subtracted from the computed sampleposition. A practical example is to subtract the value that correspondsto the length of a dynamic range control frame (which implies that theencoder has added the same value to the original sample position). Atypical example for the offset value is the temporal size of a dynamicrange control frame.

After decoding and if applicable correcting the time information of allnodes in the entire subsequent dynamic range control frame, the decoderknows how many nodes have been shifted back to the reference dynamicrange control frame (without explicitly providing this information atthe encoder) and on which sample position they are located within thereference dynamic range control frame.

The dynamic range control decoder further determines the gain valueinformation of all nodes of a received frame by decoding thedifferential gain information in the bitstream.

From the decoding step of the time information, the decoder knows howmany of the decoded gain values have to be assigned to the nodes of thereference dynamic range control frame (and to which sample position) andwhich gain values are assigned to nodes in the reference dynamic rangecontrol frame.

The decoding of the slope information and the assignment to the correctnodes are performed analogously to the decoding process of the gainvalues.

After decoding all nodes of the subsequent dynamic range control frame,it can be assured that all nodes that may be used for computing the gainvalues for each sample of the reference dynamic range control frame viainterpolation are available. After the interpolation step, the dynamicrange control gain values for each sample can be applied to thecorresponding correct audio samples.

According to an advantageous embodiment of the invention the dynamicrange control decoder is configured for identifying the one or moreshifted nodes by using the time information.

According to an advantageous embodiment of the invention the dynamicrange control decoder is configured for decoding the time information ofthe one or more shifted nodes, which is represented by a sum of a timefrom a beginning of the dynamic range control frame to which therespective node belongs to the temporal position of the respective nodewithin the dynamic range control frame to which the respective nodebelongs and an offset value being greater than or equal to a temporalsize of the dynamic range control frame subsequent to the respectivedynamic range control frame.

According to an advantageous embodiment of the invention the dynamicrange control decoder is configured for decoding the gain information ofthe bit representation of the shifted node, which is at a first positionof the bitstream portion corresponding to the dynamic range controlframe subsequent to the reference dynamic range control frame, isrepresented by an absolute gain value and wherein the gain informationof each bit representation of the shifted nodes at a position after thebit representation of the node, which is at the first position of thebitstream portion corresponding to the dynamic range control framesubsequent to the reference dynamic range control frame, is representedby a relative gain value which is equal to a difference of a gain valueof the bit representation of the respective shifted node and the gainvalue of the bit representation of the node, which precedes the bitrepresentation of the respective node

According to an advantageous embodiment of the invention the dynamicrange control decoder is configured for decoding the gain information ofthe bit representation of the node of the subsequent dynamic rangecontrol frame at a first position of the bitstream portion correspondingto the dynamic range control frame subsequent to the reference dynamicrange control frame after the one or more positions of the bitrepresentations of the one or more shifted nodes is represented by arelative gain value which is equal to a difference of a gain value ofthe bit representation of the respective node and a gain value of thebit representation of the shifted node, which precedes the bitrepresentation of the respective node.

According to an advantageous embodiment of the invention a temporal sizeof the audio frames is equal to a temporal size of the dynamic rangecontrol frames.

According to an advantageous embodiment of the invention the one or morenodes of one of the dynamic range control frames are selected from auniform time grid.

According to an advantageous embodiment of the invention each node ofthe one or more nodes comprises slope information.

According to an advantageous embodiment of the invention the dynamicrange control decoder is configured for decoding the bit representationsof the nodes using an entropy decoding technique.

The objective is further obtained by a system comprising an audioencoder device according to the invention and an audio decoder deviceaccording to the invention.

The invention further provides a method for operating an audio encoder,the method comprises the steps:

producing an encoded audio bitstream from an audio signal comprisingconsecutive audio frames;

producing an encoded dynamic range control bitstream from an dynamicrange control sequence corresponding to the audio signal and comprisingconsecutive dynamic range control frames, wherein each dynamic rangecontrol frame of the dynamic range control frames comprises one or morenodes, wherein each node of the one or more nodes comprises gaininformation for the audio signal and time information indicating towhich point in time the gain information corresponds

wherein the encoded dynamic range control bitstream comprises for eachdynamic range control frame of the dynamic range control frames acorresponding bitstream portion;

executing a shift procedure, wherein one or more nodes of the nodes ofone reference dynamic range control frame of the dynamic range controlframes are selected as shifted nodes, wherein a bit representation ofeach of the one or more shifted nodes of the one reference dynamic rangecontrol frame is embedded in the bitstream portion corresponding to thedynamic range control frame subsequent to the one reference dynamicrange control frame, wherein a bit representation of each remaining nodeof the nodes of the one reference dynamic range control frame of thedynamic range control frames is embedded into the bitstream portioncorresponding to the one reference dynamic range control frame.

The invention further provides a method for operating an audio decoder,the method comprises the steps:

decoding an encoded audio bitstream in order to reproduce an audiosignal comprising consecutive audio frames;

decoding an encoded dynamic range control bitstream in order toreproduce an dynamic range control sequence corresponding to the audiosignal and comprising consecutive dynamic range control frames;

wherein the encoded dynamic range control bitstream comprises for eachdynamic range control frame of the dynamic range control frames acorresponding bitstream portion;

wherein the encoded dynamic range control bitstream comprises bitrepresentations of nodes, wherein each bit representation of one node ofthe nodes comprises gain information for the audio signal AS and timeinformation indicating to which point in time the gain informationcorresponds; wherein the encoded dynamic range control bit streamcomprises bit representations of shifted nodes selected from the nodesof one reference dynamic range control frame of the dynamic rangecontrol frames, which are embedded in a bitstream portion correspondingto the dynamic range control frame subsequent to the one referencedynamic range control frame, wherein the bit representation of eachremaining node of the nodes of the one reference dynamic range controlframe of the dynamic range control frames is embedded into the bitstreamportion corresponding to the one reference dynamic range control frame;and

wherein the bit representation of each remaining node of the remainingnodes of the one reference dynamic range control frame of the dynamicrange control frames is decoded in order to reproduce each remainingnode of the one reference dynamic range control frame of the dynamicrange control frames;

wherein the bit representation of each shifted node of the shifted nodesselected from the nodes of the one reference dynamic range control frameof the dynamic range control frames is decoded in order to reproduceeach shifted node of the shifted nodes selected from the nodes of theone reference dynamic range control frame of the dynamic range controlframes; and

wherein the reproduced remaining nodes and the reproduced shifted nodesare combined in order to reconstruct the reference dynamic range controlframe.

In another aspect the invention provides a program for, when running ona processor, executing the method according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the appended drawings, in which:

FIG. 1 illustrates an embodiment of an audio encoder device according tothe invention in a schematic view;

FIG. 2 illustrates the principle of dynamic range control applied in thecontext of audio coding in a schematic view;

FIG. 3 illustrates the different modes for the coding of dynamic rangecontrol gain sequences in a schematic view;

FIG. 4 illustrates the application of dynamic range control in thecontext of audio coding in a schematic view;

FIG. 5 illustrates a shift procedure for nodes according to theinvention in a schematic view;

FIG. 6 illustrates the coding of time information according to theinvention in a schematic view;

FIG. 7 illustrates the coding of gain information according to theinvention in a schematic view;

FIG. 8 illustrates the coding of slope information according to theinvention in a schematic view; and

FIG. 9 illustrates an embodiment of an audio decoder device according tothe invention in a schematic view.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an embodiment of an audio encoder device 1 accordingto the invention in a schematic view. The audio encoder device 1comprises:

an audio encoder 2 configured for producing an encoded audio bitstreamABS from an audio signal AS comprising consecutive audio frames AFP,AFR, AFS;

a dynamic range control encoder 3 configured for producing an encodeddynamic range control bitstream DBS from an dynamic range controlsequence DS corresponding to the audio signal AS and comprisingconsecutive dynamic range control frames DFP, DFR, DFS, wherein eachdynamic range control frame DFP, DFR, DFS of the dynamic range controlframes DFP, DFR, DFS comprises one or more nodes A₀ . . . A₅; B₀ . . .B₂; C₀, wherein each node of the one or more nodes A₀ . . . A₅; B₀ . . .B₂; C₀ comprises gain information GA₀ . . . GA₅; GB₀ . . . GB₂; GC₀ forthe audio signal AS and time information TA₀ . . . TA₅; TB₀ . . . TB₂;TC₀ indicating to which point in time the gain information GA₀ . . .GA₅; GB₀ . . . GB₂; GC₀ corresponds;

wherein the dynamic range control encoder 3 is configured in such waythat the encoded dynamic range control bitstream DBS comprises for eachdynamic range control frame DFP, DFR, DFS of the dynamic range controlframes DFP, DFR, DFS a corresponding bitstream portion DFP′, DFR′, DFS′;

wherein the dynamic range control encoder 2 is configured for executinga shift procedure, wherein one or more nodes B₁, B₂ of the nodes B₀ . .. B₂ of one reference dynamic range control frame DFR of the dynamicrange control frames DFP, DFR, DFS are selected as shifted nodes B₁, B₂,wherein a bit representation B′₁, B′₂ of each of the one or more shiftednodes B₁, B₂ of the one reference dynamic range control frame DFR isembedded in the bitstream portion DFS' corresponding to the dynamicrange control frame DFS subsequent to the one reference dynamic rangecontrol frame DFR, wherein a bit representation B′₀ of each remainingnode B₀ of the nodes B₀ . . . B₂ of the one reference dynamic rangecontrol frame DFR of the dynamic range control frames DFP, DFR, DFS isembedded into the bitstream portion DFR′ corresponding to the onereference dynamic range control frame DFR. The invention allowscontrolling the peak bitrate that may be used for a reference dynamicrange control frame DFR without changing the resulting bitstreamsequence DBS compared to the case where the proposed method is not used.The proposed approach exploits the inherent delay of one frameintroduced by state-of-the-art audio coders to reduce peaks of number ofnodes within one frame by distributing the transmission of some of thenodes to the next subsequent dynamic range control frame. The details ofthe proposed method are presented in the following.

As explained above, when combined with an audio coding scheme thatintroduces a frame delay relative to the dynamic range control gains,the decoded dynamic range control gains are delayed by one frame beforebeing applied to the audio signal. This means that the nodes of thereference dynamic range control frame are applied to the valid audiodecoder output at dynamic range control frame subsequent to thereference dynamic range control frame. This implies that in the defaultdelay mode it is sufficient to transmit the nodes of the referencedynamic range control frame together with the nodes of the dynamic rangecontrol frame subsequent to the reference dynamic range control frameand apply the corresponding dynamic range control gains without a delaydirectly to the corresponding audio output signal at the decoder.

This fact is exploited in the invention in order to reduce the maximumnumber of nodes transmitted within one dynamic range control frame.According to the invention some of the nodes of the reference dynamicrange control frame are shifted to the subsequent dynamic range controlframe, which may be done before encoding. As it will be discussed in thefollowing, the shifted nodes may be “preceding” the first node in thesubsequent dynamic range control frame only for the encoding of the gaindifferences and the slope information. For the coding of the timedifference information, a different method may be applied.

In the example shown in FIG. 1 the preceding dynamic range control frameDFP contains six nodes A₀ . . . A₅ of which the nodes A₄, A₅ are shiftedinto the bitstream portion DFR′. Furthermore, the reference dynamicrange control frame DFR contains three nodes B₀ . . . B₂. The sum of thenumber of the shifted nodes A₄, A₅ and the nodes B₀ . . . B₂ of thereference dynamic range control frame DFR is equal to five which isbigger than the number of the nodes C₀ of the subsequent dynamic rangecontrol frame DFS so that a shift procedure is initiated in such waythat nodes B₁, B₂ are shifted into the bitstream portion DFS′. Althoughthe maximum number of nodes within the dynamic range control frames DFS,DFR, DFP is equal to six, is the maximum number of nodes within thebitstream portions DFS′, DFR′, DFP′ own equal to four so that bitstreampeak is avoided.

According to an advantageous embodiment of the invention a temporal sizeof the audio frames AFP, AFR, AFS is equal to a temporal size of thedynamic range control frames DFP, DFR, DFS.

According to an advantageous embodiment of the invention the one or morenodes A₀ . . . A₅; B₀ . . . B₂; C₀ of one of the dynamic range controlframe DFP, DFR, DFS are selected from a uniform time grid.

According to an advantageous embodiment of the invention the dynamicrange control encoder 3 is configured for encoding the nodes A₀ . . .A₅; B₀ . . . B₂; C₀ using an entropy encoding technique.

In a further aspect the invention provides a method for operating anaudio encoder 1, the method comprises the steps:

producing an encoded audio bitstream ABS from an audio signal AScomprising consecutive audio frames AFP, AFR, AFS;

producing an encoded dynamic range control bitstream DBS from an dynamicrange control sequence DS corresponding to the audio signal AS andcomprising consecutive dynamic range control frames DFP, DFR, DFS,wherein each dynamic range control frame DFP, DFR, DFS of the dynamicrange control frames DFP, DFR, DFS comprises one or more nodes A₀ . . .A₅; B₀ . . . B₂; C₀, wherein each node of the one or more nodes A₀ . . .A₅; B₀ . . . B₂; C₀ comprises gain information GA₀ . . . GA₅; GB₀ . . .GB₂; GC₀ for the audio signal AS and time information TA₀ . . . TA₅; TB₀. . . TB₂; TC₀ indicating to which point in time the gain informationcorresponds

wherein the encoded dynamic range control bitstream DBS comprises foreach dynamic range control frame DFP, DFR, DFS of the dynamic rangecontrol frames DFP, DFR, DFS a corresponding bitstream portion DFP′,DFR′, DFS′;

executing a shift procedure, wherein one or more nodes B₁, B₂ of thenodes B₀ . . . B₂ of one reference dynamic range control frame DFR ofthe dynamic range control frames DFP, DFR, DFS are selected as shiftednodes B₁, B₂, wherein a bit representation B′₁, B′₂ of each of the oneor more shifted nodes B₁, B₂ of the one reference dynamic range controlframe DFR is embedded in the bitstream portion DFS' corresponding to thedynamic range control frame DFS subsequent to the one reference dynamicrange control frame DFR, wherein a bit representation B′₀ of eachremaining node B₀ of the nodes B₀ . . . B₂ of the one reference dynamicrange control frame DFR of the dynamic range control frames DFP, DFR,DFS is embedded into the bitstream portion DFR′ corresponding to the onereference dynamic range control frame DFR.

FIG. 2 illustrates the principle of dynamic range control applied in thecontext of audio coding in a schematic view.

The process of applying DRC to a signal can be expressed by a simplemultiplication of the audio signal x(k) by a time-variant gain valueg(k):

y(k)=g(k)×(k)  (1)

where k denotes a sample time index. The value of the gain g(k) iscomputed, e.g. based on a short-term estimate of the root-mean square ofthe input signal x(k). More details about strategies to determinesuitable gains values are discussed in [1]. In the following we refer tothe time-variant gains g(k) as a gain sequence.

The invention refers to an application scenario, where both, the audiosignal AS and the dynamic range control sequence DS are coded andtransmitted. In this case, the dynamic range control gains are notdirectly applied to the audio signal AS, but encoded and transmittedtogether with the encoded audio signal ABS. At the decoder 4, both, theaudio signal AS and the dynamic range control sequence DS are decodedand the dynamic range control information is applied to thecorresponding audio signal AS.

In one aspect the invention provides a system comprising an audioencoder device 1 according to the invention and an audio decoder device4 according to the invention.

FIG. 3 illustrates the different modes for the coding of dynamic rangecontrol gain sequences in a schematic view, namely the full-frame mode(A) and delay mode (B). Gain nodes received in frame n are shown ascircles and gain nodes received frame n+1 are shown as squares. Thesolid line illustrates the interpolated DRC gain up to DRC frame n+1.

In principle, the dynamic range control encoder/decoder chain can beoperated in two modes. The so-called full-frame mode refers to the casewhere after decoding of a received dynamic range control bitstream,corresponding to a specific dynamic range control frame, the gains ateach sample position of the dynamic range control frame can beimmediately determined after interpolation based on the decoded nodes.This implies that a node has to be transmitted at each frame border,i.e., at the sample position corresponding to the last sample of thedynamic range control frame. If the dynamic range control frame lengthis N this means the last transmitted node has to be located at thesample position N within that frame. This is illustrated at the top inFIG. 3 denoted by “A”. As shown, the dynamic range control gains of thenth frame can immediately be applied to the corresponding audio frame.

The second mode is referred to as “delay mode” and it is illustrated inthe lower part “B” of FIG. 3. In this case, there is no node transmittedfor the last sample position within frame n. Therefore, the DRC decoderhas to wait for decoding the DRC frame n+1 in order to perform theinterpolation that may be used of all gain values following the lastnode within frame n. This is because the information of the first nodeof frame n+1 has to be known to perform the interpolation between thelast node of frame n and the first node in frame n+1 in order todetermine the gain value in between via interpolation.

FIG. 4 illustrates the application of dynamic range control in thecontext of audio coding in a schematic view where the audio coderintroduces one frame delay relative to the dynamic range coding scheme.

FIG. 5 illustrates a shift procedure for nodes according to theinvention in a schematic view. The left-hand side shows the situationwhen using a state-of-the-art approach, whereas the right-hand sideshows the proposed method, where each square corresponds to a node A₀ .. . A₅; B₀ . . . B₂; C₀.

According to an advantageous embodiment of the invention the shiftprocedure is initiated in case that a number of the nodes B₀ . . . B₂ ofthe reference dynamic range control frame DFR is greater than apredefined threshold value.

According to an advantageous embodiment of the invention the shiftprocedure is initiated in case that a sum of a number of the nodes B₀ .. . B₂ of the reference dynamic range control frame DFR and a number ofshifted nodes A₄, A₅ from the dynamic range control frame DFP precedingthe reference dynamic range control frame DFR to be embedded in thebitstream portion DFR′ corresponding to the reference dynamic rangecontrol frame DFR is greater than a predefined threshold value.

According to an advantageous embodiment of the invention the shiftprocedure is initiated in case that a sum of a number of the nodes B₀ .. . B₂ of the reference dynamic range control frame DFR and a number ofshifted nodes A₄, A₅ from the dynamic range control frame DFP precedingthe reference dynamic range control frame DFR to be embedded in thebitstream portion DFR′ corresponding to the reference dynamic rangecontrol frame DFR is greater than a number of the nodes C₀ of thedynamic range control frame DFS subsequent to the reference dynamicrange control frame DFR.

As explained above, when combined with an audio coding scheme thatintroduces a frame delay relative to the dynamic range control frames,the decoded dynamic range control gains are delayed by one frame beforebeing applied to the audio signal. Considering the left-hand side inFIG. 5, this means that the nodes A_(i) of the nth frame are applied tothe valid audio decoder output at frame n+1. This implies that in thedefault delay mode it would be sufficient to transmit the nodes A_(i)together with the node B₀ in frame n+1 and apply the corresponding DRCgains without a delay directly to the corresponding audio output signalat the decoder.

This fact is exploited in the proposed method to reduce the maximumnumber of nodes transmitted within one frame. This is illustrated on theright-hand side in FIG. 4. The nodes A₄ and A₅ are shifted to frame n+1before encoding, i.e., the maximum number of nodes in frame n is reducedfrom 6 to 4 in the given example. As it will be discussed in thefollowing, the nodes A₄ and A₅ are “preceding” the first node in framen+1, i.e., B₀ only for the encoding of the gain differences and theslope information. For the coding of the time difference information, adifferent method has to be applied.

FIG. 6 illustrates the coding of time information according to theinvention in a schematic view.

According to an advantageous embodiment of the invention the timeinformation TA₀ . . . TA₅; TB₀ . . . TB₂; TC₀ of the one or more nodesA₀ . . . A₅; B₀ . . . B₂; C₀ is represented in such way that the one ormore shifted nodes A₄, A₅; B₁, B₂ may be identified by using the timeinformation TA₄, TA₅; TB₁, TB₂.

According to an advantageous embodiment of the invention the timeinformation TA₄, TA₅; TB₁, TB₂ of the one or more shifted nodes A₄, A₅;B₁, B₂ is represented by a sum of a time difference t_A₄, t_A₅; t_B₁,t_B₂ from a beginning of the dynamic range control frame DFP; DFR towhich the respective node A₄, A₅; B₁, B₂ belongs to the temporalposition of the respective node A₄, A₅; B₁, B₂ within the dynamic rangecontrol frame DFP; DFR to which the respective node A₄, A₅; B₁, B₂belongs and an offset value drcFrameSize being greater than or equal toa temporal size of the dynamic range control frame DFR; DFS subsequentto the respective dynamic range control frame DFP; DFR.

First we consider the encoding of the time differences between pairs ofnodes. In FIG. 6 the situation for determining the time differences forpairs of nodes is depicted for the example according to FIG. 4, wheret_A_(i) denotes the sample position of node A_(i) on the grid ofpossible node positions within a frame. As discussed earlier nodes canbe selected on a uniform time grid, where the spacing of this griddefines the highest available time resolution deltaTmin. Thus, the timeinformation t_A_(i) is given in samples, where the time differencesbetween two nodes are integer multiples of deltaTmin.

The temporal position information of a node is encoded in a differentialway, i.e., relative to the position of the previous node. If a node isthe first node within a frame, the time difference is determinedrelative to the beginning of a frame. The left-hand side of FIG. 6depicts the situation if no node shifting is applied. In this case, thedifferential time information of node A₄ tDrcDelta_A₄ is computed astDrcDelta_A₄=t_A₄−t_A₃. This differential time value is then encodedusing the corresponding entry in an appropriate Huffman table, e.g.according to Table 1 or 2. As another example we look at the encodedtime difference of node B₀. Since it is the first node of frame n+1, thecorresponding time difference is determined relative to the beginning ofthe frame, i.e. tDrcDelta_B₀=t_B₀.

Let us now consider the encoding of the node position for the proposednode reservoir technique using node shifting. For the example shown onthe right-hand side of FIG. 6, the nodes A₄ and A₅ have been shifted tothe next frame for encoding. The representation of nodes A₀ to A₃ hasnot changed and the encoded time differences are therefore also notchanged. The same is true for the encoded position information of nodeB₀. However, the time information of node A₄ and node A₅ is nowprocessed differently. As shown in FIG. 6, the original value t_A₄indicating the sample position of node A₄ is modified at the encoder byadding an offset of drcFrameSize. Since the resulting positioninformation exceeds the maximum value that would be possible in case ofregular encoding, the offset indicates the decoder that thecorresponding node has to be further processed within the context of theprevious frame. Furthermore, the decoder knows that the original sampleposition t_A₄ is obtained by subtracting the offset drcFrameSize fromthe decoded value.

Next, we consider the computation of the time difference informationthat is actually encoded for the situation shown on the right-hand sideof FIG. 6. For coding efficiency reasons, the differential positioninformation for node A₄ is computed relative to node B₀. In contrast tothe situation previously discussed for the left-hand side of FIG. 6, thedifferential time information is now computed according totDrcDelta_A₄=t_A₄+drcFrameSize−t_B₀, i.e., by including the offset.Analogously, for node A₅ we obtaintDrcDelta_A₅=t_A₅+drcFrameSize−t_A₄−drcFrameSize, which obviously is thesame as tDrcDelta_A₅=t_A₅−t_A₄. These differential time values areencoded using the corresponding code word entry of the correct Huffmantable, e.g. according to Table 1 or 2.

The method for decoding the temporal position information can besummarized as follows. The decoder extracts the time differenceinformation of a node based on the corresponding code word from thebitstream. The time information is obtained by adding the timedifference information to the time information of the previous node. Ifthe resulting sample position is larger than drcFrameSize the decoderknows that the present node has to be processed as if it were the lastnode in the previous frame, i.e., it has to be appended to the nodesdecoded in the previous frame. The correct sample position is determinedby subtracting the offset value drcFrameSize from the decoded timevalue. The same processing steps are applied in an analog way if moreshifted nodes occur in a decoded frame.

After decoding and correcting the time information of an entire frame,the decoder knows how many nodes have been shifted back to the previousframe (without explicitly providing this information at the encoder) andon which sample position they are located within the previous frame. Theinformation about the number of shifted nodes will be further exploitedin the context of decoding gain and slope information described below.

FIG. 7 illustrates the coding of gain information according to theinvention in a schematic view.

According to an advantageous embodiment of the invention the gaininformation GB₁ of the bit representation B′₁ of the shifted node B₁,which is at a first position of the bitstream portion DFS' correspondingto the dynamic range control frame DFS subsequent to the referencedynamic range control frame DFR, is represented by an absolute gainvalue g_B₁ and wherein the gain information GB₂ of each bitrepresentation B′₂ of the shifted nodes B₂ at a position after the bitrepresentation B′₁ of the node B₁, which is at the first position of thebitstream portion DFS' corresponding to the dynamic range control frameDFS subsequent to the reference dynamic range control frame DFR, isrepresented by a relative gain value which is equal to a difference of again value g_B₂ of the bit representation B′₂ of the respective shiftednode B₂ and the gain value g_B₁ of the bit representation B′₁ of thenodeB₁, which precedes the bit representation B′₂ of the respectivenodeB₂.

According to an advantageous embodiment of the invention, in case thatthe bit representations B′₁, B′₂ of one or more shifted nodes B₁, B₂ ofthe reference dynamic range control frame DFR is embedded in thebitstream portion DFS' corresponding to the dynamic range control frameDFS subsequent to the reference dynamic range control frame DFR, thegain information GC₀ of the bit representation C′₀ of the node C₀ of thesubsequent dynamic range control frame DFS at a first position of thebitstream portion DFS' corresponding to the dynamic range control frameDFS subsequent to the reference dynamic range control frame DFR afterthe one or more positions of the bit representations B′₁, B′₂ of the oneor more shifted nodes B₁, B₂ is represented by a relative gain valuewhich is equal to a difference of a gain value g_C₀ of the bitrepresentation C′₀ of the respective node C₀ and a gain value g_B₂ ofthe bit representation B′₂ of the shifted nodeB₂, which precedes the bitrepresentation C′₀ of the respective node C₀.

In FIG. 7 the situation for determining the gain differences for pairsof nodes is depicted for the example according to FIG. 5, where g_A_(i)denotes the gain value of node A_(i).

First, the differential gain values for the node A₄ is considered. Forthe approach without node reservoir, depicted on the left-hand side ofFIG. 7, the differential gain value gain Delta_A₄ is computed from thedifference of the gain value (in dB) of the preceding node A₃ and thenode A₄, i.e., gain-Delta_A₄=g_A₄−g_A₃. This differential gain value isthen encoded using the corresponding entry in an appropriate Huffmantable. Furthermore, we consider the first node of frame n+1 on theleft-hand side of FIG. 7. Since B₀ is the first node of that frame, itgain value is not encoded in a differential way, but according to aspecific coding of initial gain values gainInitial, i.e., the gain valueis encoded as its actual value: gainDelta_B₀=g_B₀.

For the situation shown on the right-hand side, where the node A₄ hasbeen shifted to the next frame n+1, the values of the encoded gaininformation is different. As can be seen, after being shifted, the nodeA₄ becomes the first node in frame n+1 with respect to encoding the gaindifferences. Thus, its gain value is not encoded in a differential way,but the specific coding of initial gain values is applied as describedabove. The differential gain value of A₅ will remain the same for bothsituations shown on the left- and the right-hand side. Since node B₀ nowfollows node A₅ if the node reservoir is used, its gain information willbe determined from the difference of the gains of node B₀ and A₅, i.e.,gainDelta_B₀=g_B₀·g_A₅. Note that only the way how the gain differencesare determined changes when applying the node reservoir technique,whereas the reconstructed values of the gains remain the same for eachnode. Obviously, after decoding the entire gain related information ofthe frames n and n+1, the obtained gain values for the nodes A₀ to B₀are identical to that obtained in the left-hand side, and the nodes canbe computed “in time” for application of the DRC gains to thecorresponding audio frame.

As discussed in the previous paragraph, the number of shifted nodes andtheir sample position within the previous frame are known after decodingthe time difference information. As illustrated on the right-hand sideof FIG. 6, the gain values of shifted nodes from frame n startimmediately from the beginning of the received gain information of framen+1. Therefore, the information on the number of shifted nodes issufficient for the decoder to assign each gain value to the correctsample position within the correct frame. Considering the example shownon the right-hand side in FIG. 6, the decoder knows that the first twodecoded gain values of frame n+1 have to be appended to the last gainvalues of the previous frame, whereas the third gain value correspondsto the correct gain value of the first node in the current frame.

FIG. 8 illustrates the coding of slope information according to theinvention in a schematic view.

According to an advantageous embodiment of the invention each node A₀ .. . A₅; B₀ . . . B₂; C₀ of the one or more nodes comprises A₀ . . . A₅;B₀ . . . B₂; C₀ slope information SA₀ . . . SA₅; SB₀ . . . SB₂; SC₀.

Next, the coding of slope information is considered, which isillustrated in FIG. 8. The slope information of the nodes isn't encodedin a differential way between pairs of nodes, but for each nodeindependently. Therefore, the slope related information remainsunchanged in both cases with and without usage of the node reservoir. Asin case of coding of gain values, the Huffman tables for generating thecode words for slope information remain the same for both cases, withand without using the proposed node shifting. The assignment of theslope information to the correct sample position within the correctframe is performed analogously to the case of decoding the gain values.

After all nodes information received for frame n+1 have been decoded andif applicable shifted back to the preceding frame n, the gaininterpolation for frame n using splines or linear interpolation can beperformed in the common way and the gain values are applied to thecorresponding audio frame.

FIG. 9 illustrates an embodiment of an audio decoder device according tothe invention in a schematic view. The audio decoder device 4 comprises:

an audio decoder 5 configured for decoding an encoded audio bitstreamABS in order to reproduce an audio signal AS comprising consecutiveaudio frames AFP, AFR, AFS;

a dynamic range control decoder 6 configured for decoding an encodeddynamic range control bitstream DBS in order to reproduce an dynamicrange control sequence DS corresponding to the audio signal AS andcomprising consecutive dynamic range control frames DFP, DFR, DFS;

wherein the encoded dynamic range control bitstream DBS comprises foreach dynamic range control frame DFP, DFR, DFS of the dynamic rangecontrol frames a corresponding bitstream portion DFP′, DFR′, DFS′;

wherein the encoded dynamic range control bitstream DBS comprises bitrepresentations A′₀ . . . A′₅; B′₀ . . . B′₂; C′₀ of nodes A₀ . . . A₅;B₀ . . . B₂; C₀, wherein each bit representation of one node of thenodes comprises gain information GA₀ . . . GA₅; GB₀ . . . GB₂; GC₀ forthe audio signal AS and time information TA₀ . . . TA₅; TB₀ . . . TB₂;TC₀ indicating to which point in time the gain information GA₀ . . .GA₅; GB₀ . . . GB₂; GC₀ corresponds;

wherein the encoded dynamic range control bit stream DBS comprises bitrepresentations B′₁, B′₂ of shifted nodes B₁, B₂ selected from the nodesB₀ . . . B₂ of one reference dynamic range control frame DFR of thedynamic range control frames DFP, DFR, DFS, which are embedded in abitstream portion corresponding to the dynamic range control frame DFSsubsequent to the one reference dynamic range control frame DFR, whereinthe bit representation B′₀ of each remaining node B₀ of the nodes B₀ . .. B₂ of the one reference dynamic range control frame DFR of the dynamicrange control frames DFP, DFR, DFS is embedded into the bitstreamportion DFR′ corresponding to the one reference dynamic range controlframe DFR; and

wherein the dynamic range control decoder 6 is configured for decodingthe bit representation B′₀ of each remaining node B₀ of the remainingnodes B′₀ of the one reference dynamic range control frame DFR of thedynamic range control frames DFP, DFR, DFS in order to reproduce eachremaining node B₀ of the one reference dynamic range control frame DFRof the dynamic range control frames DFP, DFR, DFS, for decoding the bitrepresentation B′₁, B′₂ of each shifted node B₁, B₂ of the shifted nodesB₁, B₂ selected from the nodes B₀ . . . B₂ of the one reference dynamicrange control frame DFR of the dynamic range control frames DFP, DFR,DFS in order to reproduce each shifted node B₁, B₂ of the shifted nodesB₁, B₂ selected from the nodes of the one reference dynamic rangecontrol frame DFR of the dynamic range control frames DFP, DFR, DFS andfor combining the reproduced remaining nodes B₀ and the reproducedshifted nodes B₁, B₂ in order to reconstruct the reference dynamic rangecontrol frame DFR.

According to an advantageous embodiment of the invention the dynamicrange control decoder 6 is configured for identifying the one or moreshifted nodes A₄, A₅; B₁, B₂ by using the time information TA₄, TA₅;TB₁, TB₂.

According to an advantageous embodiment of the invention the dynamicrange control decoder 6 is configured for decoding the time informationTA₄, TA₅; TB₁, TB₂ of the one or more shifted nodes A₄, A₅; B₁, B₂,which is represented by a sum of a time difference t_A₄, t_A₅; t_B₁,t_B₂ from a beginning of the dynamic range control frame DFP; DFR towhich the respective node A₄, A₅; B₁, B₂ belongs to the temporalposition of the respective node A₄, A₅; B₁, B₂ within the dynamic rangecontrol frame DFP; DFR to which the respective node A₄, A₅; B₁, B₂belongs and an offset value drcFrameSize being greater than or equal toa temporal size of the dynamic range control frame DFR; DFS subsequentto the respective dynamic range control frame DFP; DFR.

According to an advantageous embodiment of the invention the dynamicrange control decoder 6 is configured for decoding the gain informationGB₁ of the bit representation B′₁ of the shifted node B₁, which is at afirst position of the bitstream portion DFS' corresponding to thedynamic range control frame DFS subsequent to the reference dynamicrange control frame DFR, is represented by an absolute gain value g_B₁and wherein the gain information GB₂ of each bit representation B′₂ ofthe shifted nodes B₂ at a position after the bit representation B′₁ ofthe node B₁, which is at the first position of the bitstream portionDFS' corresponding to the dynamic range control frame DFS subsequent tothe reference dynamic range control frame DFR, is represented by arelative gain value which is equal to a difference of a gain value g_B₂of the bit representation B′₂ of the respective shifted node B₂ and thegain value g_B₁ of the bit representation B′₁ of the nodeB₁, whichprecedes the bit representation B′₂ of the respective nodeB₂

According to an advantageous embodiment of the invention the dynamicrange control decoder 6 is configured for decoding the gain informationGC₀ of the bit representation C′₀ of the node C₀ of the subsequentdynamic range control frame DFS at a first position of the bitstreamportion DFS' corresponding to the dynamic range control frame DFSsubsequent to the reference dynamic range control frame DFR after theone or more positions of the bit representations B′₁, B′₂ of the one ormore shifted nodes B₁, B₂ is represented by a relative gain value whichis equal to a difference of a gain value g_C₀ the bit representation C′₀of the respective node C₀ and the gain value g_B₂ of the bitrepresentation B′₂ of the shifted nodeB₂, which precedes the bitrepresentation C′₀ of the respective node C₀.

According to an advantageous embodiment of the invention a temporal sizeof the audio frames AFP, AFR, AFS is equal to a temporal size of thedynamic range control frames AFP, AFR, AFS.

According to an advantageous embodiment of the invention the one or morenodes A₀ . . . A₅; B₀ . . . B₂; C₀ of one of the dynamic range controlframes DFP, DFR, DFS are selected from a uniform time grid.

According to an advantageous embodiment of the invention each node A₀ .. . A₅; B₀ . . . B₂; C₀ of the one or more nodes A₀ . . . A₅; B₀ . . .B₂; C₀ comprises slope information SA₀ . . . SA₅; SB₀ . . . SB₂; SC₀.

According to an advantageous embodiment of the invention the dynamicrange control decoder 6 is configured for decoding the bitrepresentations of the nodes A′₀ . . . A′₅; B′₀ . . . B′₂; C′₀ using anentropy decoding technique.

In another aspect the invention provides a method for operating an audiodecoder, the method comprises the steps:

decoding an encoded audio bitstream ABS in order to reproduce an audiosignal AS comprising consecutive audio frames AFP, AFR, AFS;

decoding an encoded dynamic range control bitstream DBS in order toreproduce an dynamic range control sequence DS corresponding to theaudio signal AS and comprising consecutive dynamic range control framesDFP, DFR, DFS;

wherein the encoded dynamic range control bitstream DBS comprises foreach dynamic range control frame DFP, DFR, DFS of the dynamic rangecontrol frames a corresponding bitstream portion DFP′, DFR′, DFS′;

wherein the encoded dynamic range control bitstream DBS comprises bitrepresentations A′₀ . . . A′₅; B′₀ . . . B′₂; C′₀ of nodes A₀ . . . A₅;B₀ . . . B₂; C₀, wherein each bit representation of one node of thenodes comprises gain information GA₀ . . . GA₅; GB₀ . . . GB₂; GC₀ forthe audio signal AS and time information TA₀ . . . TA₅; TB₀ . . . TB₂;TC₀ indicating to which point in time the gain information GA₀ . . .GA₅; GB₀ . . . GB₂; GC₀ corresponds;

wherein the encoded dynamic range control bit stream DBS comprises bitrepresentations B′₁, B′₂ of shifted nodes B₁, B₂ selected from the nodesB₀ . . . B₂ of one reference dynamic range control frame DFR of thedynamic range control frames DFP, DFR, DFS, which are embedded in abitstream portion corresponding to the dynamic range control frame DFSsubsequent to the one reference dynamic range control frame DFR, whereinthe bit representation B′₀ of each remaining node B₀ of the nodes B₀ . .. B₂ of the one reference dynamic range control frame DFR of the dynamicrange control frames DFP, DFR, DFS is embedded into the bitstreamportion DFR′ corresponding to the one reference dynamic range controlframe DFR; and

wherein the bit representation B′₀ of each remaining node B₀ of theremaining nodes B′₀ of the one reference dynamic range control frame DFRof the dynamic range control frames DFP, DFR, DFS is decoded in order toreproduce each remaining node B₀ of the one reference dynamic rangecontrol frame DFR of the dynamic range control frames DFP, DFR, DFS;

wherein the bit representation B′₁, B′₂ of each shifted node B₁, B₂ ofthe shifted nodes B₁, B₂ selected from the nodes B₀ . . . B₂ of the onereference dynamic range control frame DFR of the dynamic range controlframes DFP, DFR, DFS is decoded in order to reproduce each shifted nodeB₁, B₂ of the shifted nodes B₁, B₂ selected from the nodes of the onereference dynamic range control frame DFR of the dynamic range controlframes DFP, DFR, DFS; and

wherein the reproduced remaining nodes B₀ and the reproduced shiftednodes B₁, B₂ are combined in order to reconstruct the reference dynamicrange control frame DFR.

With respect to the decoder, the encoder and the methods of thedescribed embodiments the following shall be mentioned:

Although some aspects have been described in the context of anapparatus, it is clear that these aspects also represent a descriptionof the corresponding method, where a block or device corresponds to amethod step or a feature of a method step. Analogously, aspectsdescribed in the context of a method step also represent a descriptionof a corresponding block or item or feature of a correspondingapparatus.

Depending on certain implementation requirements, embodiments of theinvention can be implemented in hardware or in software. Theimplementation can be performed using a digital storage medium, forexample a floppy disk, a DVD, a CD, a ROM, a PROM, an EPROM, an EEPROMor a FLASH memory, having electronically readable control signals storedthereon, which cooperate (or are capable of cooperating) with aprogrammable computer system such that the respective method isperformed.

Some embodiments according to the invention comprise a data carrierhaving electronically readable control signals, which are capable ofcooperating with a programmable computer system such that one of themethods described herein is performed.

Generally, embodiments of the present invention can be implemented as acomputer program product with a program code, the program code beingoperative for performing one of the methods when the computer programproduct runs on a computer. The program code may for example be storedon a machine readable carrier.

Other embodiments comprise the computer program for performing one ofthe methods described herein, which is stored on a machine readablecarrier or a non-transitory storage medium.

In other words, an embodiment of the inventive method is, therefore, acomputer program having a program code for performing one of the methodsdescribed herein, when the computer program runs on a computer.

A further embodiment of the inventive methods is, therefore, a datacarrier (or a digital storage medium, or a computer-readable medium)comprising, recorded thereon, the computer program for performing one ofthe methods described herein.

A further embodiment of the inventive method is, therefore, a datastream or a sequence of signals representing the computer program forperforming one of the methods described herein. The data stream or thesequence of signals may be configured, for example, to be transferredvia a data communication connection, for example via the Internet.

A further embodiment comprises a processing means, for example acomputer, or a programmable logic device, configured or adapted toperform one of the methods described herein.

A further embodiment comprises a computer having installed thereon thecomputer program for performing one of the methods described herein.

In some embodiments, a programmable logic device (for example a fieldprogrammable gate array) may be used to perform some or all of thefunctionalities of the methods described herein. In some embodiments, afield programmable gate array may cooperate with a microprocessor inorder to perform one of the methods described herein. Generally, themethods are advantageously performed by any hardware apparatus.

While this invention has been described in terms of several embodiments,there are alterations, permutations, and equivalents which fall withinthe scope of this invention. It should also be noted that there are manyalternative ways of implementing the methods and compositions of thepresent invention. It is therefore intended that the following appendedclaims be interpreted as including all such alterations, permutationsand equivalents as fall within the true spirit and scope of the presentinvention.

REFERENCES

-   [1] D. Giannoulis, M. Massberg, J. D. Reiss, “Digital Dynamic Range    Compressor Design—A Tutorial and Analysis” J. Audio Engineering    Society, Vol. 60, No. 6, June 2012. in

1. An audio encoder device comprising: an audio encoder configured forproducing an encoded audio bitstream from an audio signal comprisingconsecutive audio frames; a dynamic range control encoder configured forproducing an encoded dynamic range control bitstream from an dynamicrange control sequence corresponding to the audio signal and comprisingconsecutive dynamic range control frames, wherein each dynamic rangecontrol frame of the dynamic range control frames comprises one or morenodes, wherein each node of the one or more nodes comprises gaininformation for the audio signal and time information indicating towhich point in time the gain information corresponds; wherein thedynamic range control encoder is configured in such way that the encodeddynamic range control bitstream comprises for each dynamic range controlframe of the dynamic range control frames a corresponding bitstreamportion; wherein the dynamic range control encoder is configured forexecuting a shift procedure, wherein one or more nodes of the nodes ofone reference dynamic range control frame of the dynamic range controlframes are selected as shifted nodes, wherein a bit representation ofeach of the one or more shifted nodes of the one reference dynamic rangecontrol frame is embedded in the bitstream portion corresponding to thedynamic range control frame subsequent to the one reference dynamicrange control frame.
 2. The audio encoder device according to claim 1,wherein a bit representation of each remaining node of the nodes of theone reference dynamic range control frame of the dynamic range controlframes is embedded into the bitstream portion corresponding to the onereference dynamic range control frame.
 3. The audio encoder deviceaccording to claim 1, wherein the shift procedure is initiated in casethat a number of the nodes of the reference dynamic range control frameis greater than a predefined threshold value.
 4. The audio encoderdevice according to claim 1, wherein the shift procedure is initiated incase that a sum of a number of the nodes of the reference dynamic rangecontrol frame and a number of shifted nodes from the dynamic rangecontrol frame preceding the reference dynamic range control frame to beembedded in the bitstream portion corresponding to the reference dynamicrange control frame is greater than a predefined threshold value.
 5. Theaudio encoder device according to claim 1, wherein the shift procedureis initiated in case that a sum of a number of the nodes of thereference dynamic range control frame and a number of shifted nodes fromthe dynamic range control frame preceding the reference dynamic rangecontrol frame to be embedded in the bitstream portion corresponding tothe reference dynamic range control frame is greater than a number ofthe nodes of the dynamic range control frame subsequent to the referencedynamic range control frame.
 6. The audio encoder device according toclaim 1, wherein the time information of the one or more nodes isrepresented in such way that the one or more shifted nodes may beidentified by using the time information.
 7. The audio encoder deviceaccording to claim 6, wherein the time information of the one or moreshifted nodes is represented by a sum of a time difference from abeginning of the dynamic range control frame to which the respectivenode belongs to the temporal position of the respective node within thedynamic range control frame to which the respective node belongs and anoffset value being greater than or equal to a temporal size of thedynamic range control frame subsequent to the respective dynamic rangecontrol frame.
 8. The audio encoder device according to claim 1, whereinthe gain information of the bit representation of the shifted node,which is at a first position of the bitstream portion corresponding tothe dynamic range control frame subsequent to the reference dynamicrange control frame, is represented by an absolute gain value andwherein the gain information of each bit representation of the shiftednodes at a position after the bit representation of the node, which isat the first position of the bitstream portion corresponding to thedynamic range control frame subsequent to the reference dynamic rangecontrol frame, is represented by a relative gain value which is equal toa difference of a gain value of the bit representation of the respectiveshifted node and a gain value of the bit representation of the node,which precedes the bit representation of the respective node.
 9. Theaudio encoder device according to claim 1, wherein, in case that the bitrepresentations of one or more shifted nodes of the reference dynamicrange control frame is embedded in the bitstream portion correspondingto the dynamic range control frame subsequent to the reference dynamicrange control frame, the gain information of the bit representation ofthe node of the subsequent dynamic range control frame at a firstposition of the bitstream portion corresponding to the dynamic rangecontrol frame subsequent to the reference dynamic range control frameafter the one or more positions of the bit representations of the one ormore shifted nodes is represented by a relative gain value which isequal to a difference of a gain value of the bit representation of therespective node and a gain value of the bit representation of theshifted node, which precedes the bit representation of the respectivenode.
 10. The audio encoder device according to claim 1, wherein atemporal size of the audio frames is equal to a temporal size of thedynamic range control frames.
 11. The audio encoder device according toclaim 1, wherein the one or more nodes of one of the dynamic rangecontrol frame are selected from a uniform time grid.
 12. The audioencoder device according to claim 1, wherein each node of the one ormore nodes comprises slope information.
 13. The audio encoder deviceaccording to claim 1, wherein the dynamic range control encoder isconfigured for encoding the nodes using an entropy encoding technique.14. An audio decoder device comprising: an audio decoder configured fordecoding an encoded audio bitstream in order to reproduce an audiosignal comprising consecutive audio frames; a dynamic range controldecoder configured for decoding an encoded dynamic range controlbitstream in order to reproduce an dynamic range control sequencecorresponding to the audio signal and comprising consecutive dynamicrange control frames; wherein the encoded dynamic range controlbitstream comprises for each dynamic range control frame of the dynamicrange control frames a corresponding bitstream portion; wherein theencoded dynamic range control bitstream comprises bit representations ofnodes, wherein each bit representation of one node of the nodescomprises gain information for the audio signal and time informationindicating to which point in time the gain information corresponds;wherein the encoded dynamic range control bit stream comprises bitrepresentations of shifted nodes selected from the nodes of onereference dynamic range control frame of the dynamic range controlframes, which are embedded in a bitstream portion corresponding to thedynamic range control frame subsequent to the one reference dynamicrange control frame; and wherein the dynamic range control decoder isconfigured for decoding the bit representation of each shifted node ofthe shifted nodes selected from the nodes of the one reference dynamicrange control frame of the dynamic range control frames in order toreproduce each shifted node of the shifted nodes selected from the nodesof the one reference dynamic range control frame of the dynamic rangecontrol frames.
 15. The audio decoder device according to claim 14,wherein the bit representation of each remaining node of the nodes ofthe one reference dynamic range control frame of the dynamic rangecontrol frames is embedded into the bitstream portion corresponding tothe one reference dynamic range control frame, wherein the dynamic rangecontrol decoder is configured for decoding the bit representation ofeach remaining node of the remaining nodes of the one reference dynamicrange control frame of the dynamic range control frames in order toreproduce each remaining node of the one reference dynamic range controlframe of the dynamic range control frames and for combining thereproduced remaining nodes and the reproduced shifted nodes in order toreconstruct the reference dynamic range control frame.
 16. The audiodecoder device according to claim 14, wherein the dynamic range controldecoder is configured for identifying the one or more shifted nodes byusing the time information.
 17. The audio decoder device according toclaim 14, wherein the dynamic range control decoder is configured fordecoding the time information of the one or more shifted nodes, which isrepresented by a sum of a time difference from a beginning of thedynamic range control frame to which the respective node belongs to thetemporal position of the respective node within the dynamic rangecontrol frame to which the respective node belongs and an offset valuebeing greater than or equal to a temporal size of the dynamic rangecontrol frame subsequent to the respective dynamic range control frame.18. The audio decoder device according to claim 14, wherein the dynamicrange control decoder is configured for decoding the gain information ofthe bit representation of the shifted node, which is at a first positionof the bitstream portion corresponding to the dynamic range controlframe subsequent to the reference dynamic range control frame, isrepresented by an absolute gain value and wherein the gain informationof each bit representation of the shifted nodes at a position after thebit representation of the node, which is at the first position of thebitstream portion corresponding to the dynamic range control framesubsequent to the reference dynamic range control frame, is representedby a relative gain value which is equal to a difference of a gain valueof the bit representation B′₂ of the respective shifted node B₂ and again value of the bit representation of the node, which precedes the bitrepresentation of the respective node
 19. The audio decoder deviceaccording to claim 14, wherein the dynamic range control decoder isconfigured for decoding the gain information of the bit representationof the node of the subsequent dynamic range control frame at a firstposition of the bitstream portion corresponding to the dynamic rangecontrol frame subsequent to the reference dynamic range control frameafter the one or more positions of the bit representations of the one ormore shifted nodes is represented by a relative gain value which isequal to a difference of a gain value of the bit representation of therespective node and a gain value of the bit representation of theshifted node, which precedes the bit representation of the respectivenode.
 20. The audio decoder device according to claim 14, wherein atemporal size of the audio frames is equal to a temporal size of thedynamic range control frames.
 21. The audio decoder device according toclaim 14, wherein the one or more nodes of one of the dynamic rangecontrol frames are selected from a uniform time grid.
 22. The audiodecoder device according to claim 14, wherein each node of the one ormore nodes comprises slope information.
 23. The audio decoder deviceaccording to claim 14, wherein the dynamic range control decoder isconfigured for decoding the bit representations of the nodes using anentropy decoding technique.
 24. A system comprising an audio encoderdevice comprising: an audio encoder configured for producing an encodedaudio bitstream from an audio signal comprising consecutive audioframes; a dynamic range control encoder configured for producing anencoded dynamic range control bitstream from an dynamic range controlsequence corresponding to the audio signal and comprising consecutivedynamic range control frames, wherein each dynamic range control frameof the dynamic range control frames comprises one or more nodes, whereineach node of the one or more nodes comprises gain information for theaudio signal and time information indicating to which point in time thegain information corresponds; wherein the dynamic range control encoderis configured in such way that the encoded dynamic range controlbitstream comprises for each dynamic range control frame of the dynamicrange control frames a corresponding bitstream portion; wherein thedynamic range control encoder is configured for executing a shiftprocedure, wherein one or more nodes of the nodes of one referencedynamic range control frame of the dynamic range control frames areselected as shifted nodes, wherein a bit representation of each of theone or more shifted nodes of the one reference dynamic range controlframe is embedded in the bitstream portion corresponding to the dynamicrange control frame subsequent to the one reference dynamic rangecontrol frame, and an audio decoder device according to claim
 14. 25. Amethod for operating an audio encoder, the method comprising: producingan encoded audio bitstream from an audio signal comprising consecutiveaudio frames; producing an encoded dynamic range control bitstream froman dynamic range control sequence corresponding to the audio signal andcomprising consecutive dynamic range control frames, wherein eachdynamic range control frame of the dynamic range control framescomprises one or more nodes, wherein each node of the one or more nodescomprises gain information for the audio signal and time informationindicating to which point in time the gain information correspondswherein the encoded dynamic range control bitstream comprises for eachdynamic range control frame of the dynamic range control frames acorresponding bitstream portion; executing a shift procedure, whereinone or more nodes of the nodes of one reference dynamic range controlframe of the dynamic range control frames are selected as shifted nodes,wherein a bit representation of each of the one or more shifted nodes ofthe one reference dynamic range control frame is embedded in thebitstream portion corresponding to the dynamic range control framesubsequent to the one reference dynamic range control frame.
 26. Amethod for operating an audio decoder, the method comprising: decodingan encoded audio bitstream in order to reproduce an audio signalcomprising consecutive audio frames; decoding an encoded dynamic rangecontrol bitstream in order to reproduce an dynamic range controlsequence corresponding to the audio signal and comprising consecutivedynamic range control frames; wherein the encoded dynamic range controlbitstream comprises for each dynamic range control frame of the dynamicrange control frames a corresponding bitstream portion; wherein theencoded dynamic range control bitstream comprises bit representations ofnodes, wherein each bit representation of one node of the nodescomprises gain information for the audio signal and time informationindicating to which point in time the gain information corresponds;wherein the encoded dynamic range control bit stream comprises bitrepresentations of shifted nodes selected from the nodes of onereference dynamic range control frame of the dynamic range controlframes, which are embedded in a bitstream portion corresponding to thedynamic range control frame subsequent to the one reference dynamicrange control frame; and wherein the bit representation of each shiftednode of the shifted nodes selected from the nodes of the one referencedynamic range control frame of the dynamic range control frames isdecoded in order to reproduce each shifted node of the shifted nodesselected from the nodes of the one reference dynamic range control frameof the dynamic range control frames.
 27. A non-transitory digitalstorage medium having a computer program stored thereon to perform themethod according to claim
 25. 28. A non-transitory digital storagemedium having a computer program stored thereon to perform the methodaccording to claim 26.